Battery liner



Patented Nov. 30, 1926.

UNITED STATES PATENT. OFFICE.

ARLIE WILLIAM SCI-IORGER, OF MADISON, WISCONSIN, ASSIGNOR, BY MESNE AS- SIGNMENTS, TO 0; F. BURGESS LABORATORIES, 1110., 0! DOVER, DELAWARE, A COR- PORATION OF DELAWARE.

No Drawing.

In the manufacture of dry cells 6 high or higher, and of the type commonlyused with telephones, or for gas enginelgn t on, or in the filament circuit of radio receivingsets, it is common practice to place a sheet of paper board against the inner surface of the zinc can or electrode to prevent the finely til pulverized mixture of carbonaceous material and manganese dioxide, commonly known as the mix from coming in contact with the zinc and causing a short circuit. The paper board in common use at the present time for that purpose is somewhat like blotting paper in appearance and is made up of compara tively loosely adhering fibres. llt is highly porous, and in a wet condition has little strength. The pulp used for the manufacture of such paper board has the property of freeness, that is, the fibers are ungelatinized, or at most, are gelatinized or hydrated only to an insignificant amount. @wing to the nature of the pulp from which such paper board. is made and owing to the manner in which that pulp is formed into sheets, the openings between the fibres of the board are relatively large, with the result that the sheet is highly porous. It has been my experience that such sheets though easily penetrated by the battery electrolyte are porous in an irregular way with the result that electrical action at the zinc surface is inclined to be localized. and that diffusion of the electrolytic salts through the board does not occur inthe smooth and even manner essential to most efficient and reliable action of the cell.

' The paper boards of the prior art have other short comings well known to battery makers, such as the tendency to tear during assembly of the cell; the danger that fine particles of the mix will sift through the paper into contact with the zinc; the resistance oli'ered to the flow of current from one electrode to the other through the cell, and the slowness of the recuperation after a heavy service demand and resultant depletion of the electrolyte in the pores of the sheet.

I have found that if wood pulp, suchas unbleached spruce sulphite pulp, is beaten or ground with water until it acquires a high degree of hydration commonly known as wetness by paper makers. or until the BATTERY LINER,

Application filed November 22, 1923. Serial No. 676,288.

fibrous structure is in part reduced to a gel, a board made from such a pulp can be used in dry cells, particularly while still in its initial wet condition, with much improvement to the cells. The short circuit amperage of a standard or No. 6 dry cell (6" tall by 2 in diameter) can in this way be increased 10 to 20 amperes, other conditions remaining the same. Also there is a small increase in voltage, particularly on closed circuit.

Such a wet gelatinized board approximates parchment paper in the uniformity of its conductivity for electricity,.and in the uniformity with which it permits diffusion of salts. It is much more plastic than ordinary battery board, and consequently, when the mix is rammed or forcibly tamped into the zinc cup, in accordance with standard practice, there is a more continuous and intimate contact between the board and the zinc surface. In this way the electrical conductivity of the dry cell is increased and rendered more uniform. The battery board of my invention is much tougher in the wet condition than ordinary board, thus greatly decreasing the liability of rupture during tamping.

The degree of hydration or gelatinization to which the fibres should be subjected will depend upon the kind of pulp employed. and upon the apparatus used for producing gelatinization. I have satisfactorily employed ordinary paper makers heaters, though other apparatus capable of producng agrinding or beating action on the pulp in water may he used, such, for instance. as a ball mill, or a paper makers refiner."

'lVhatever form of apparatus isuscd for mechanically disintegrating the cellulosein water, it should be such as not to reduce the fibers to powder by a cutting action, but on the contrary, should be such as will bring about the desired extent of gelatinization, while preferably leaving some of the initial fibers present toform a mechanical structure within the interstices of which the gel of disintegrated fibers maybe held. The time required for producing a given degree of gelatinization with a paper maker's beater depends upon the. size of the heater, the speed of the roll, the bluntness of the knives, and the extent to which the roll is lowered upon the bed-plate. ll have, therefore, deemed it expedient to here set. forth in some detail all of the operating conditions essential or important to the production of my present battery board.

The phenomenon of gelatinization or hydration of cellulose is not sufficiently well understood at the present time to be rigidly defined.

In changing cellulose to the gelatinized or hydrated form, intra-molecular distension, hydrolysis and oxidation appear to take place with the formation of hydrocellulose, oxycellulqse' and so-called dextrins. .Fortunately it is not essential to the practice of the present invention that the exact nature of the changes should be fully known. It

can easil be demonstrated that when chemical wo pulps (cellulose) are subjected to prolonged beating in the presence of water the fibrous structure is partially or totally of cellulose, such as cotton, or as including wood fibers not entirely freed from lignin. Practically pure cellulose has approximately the formula (C H, O )n, while Wood or ligno-cellulose, on the contrary, contains approximately 30% of lignin, a compound having a higher carbon content than does cellulose and one which does not yield sugars on hydrolysis, as does cellulose. Ligno-cellulose is but slightly soluble, or soluble with great difliculty in such ordinary cellulose solvents as zinc chloride solution, Schweitzers reagent, etc.

Gelat'inized cellulose whether made from cotton or from wood and whether pure or contaminated with lignin possesses to a high degree the property of retaining a large amount of water when mechanical means such as centrifuging or pressing; are employed for removing the latter. It will commonly retain from 300 to 000 per cent of water by bone dry weight of cellulose content. Another characteristic is its resistance to penetrance by fats and oils. The two properties of gelatinized cellulose by which that material can be most easily recognized by battery makers are the high shrinkage and the hardness produced when a battery board is passed from the wet to the dry condition. ln these respects the battery board of the present invention differs from battery cumstances where the characteristics of shrinkage and hardness havebeen obscured, as through contact with battery electrolyte or because of age and progressive chemical change, other criteria may be relied on.

Although the process of manufacturing my improved battery board may varyun many details, the method used by me with best success is as follows: Wood or lignocellulose is barked, chi pod and then is cooked to a pulp'in usua manner as by the well known sulphite process. This cooking removes the li in and other natural incrusting materials and leaves the woody fibers loosely bound to one another. The fibers can then be separated in usual papermaking equipment and ultimately formed into a-pulp, which on passage through a wet machine can be reduced to the form of laps. Such laps made from sulphite pulp are a standard commodity at pulp mills and can be purchased in the open market. I have used with best success a spruce, balsam or hemlock sulphite pulp, although I am aware that other cellulose pulps may be employed. A soda-pulp from aspenis not as suitable as the above because more time and power are required to obtain the proper degree of gelatinization. The followlng data is given byway of llustration. A twenty pound beater, the roll of which has a peripheral speed of 2000 feet per second, is charged with sulphite spruce pulp and water, and the roll set down hard upon the bed-plate. Under these conditions with dull knives, a satisfactorily gelatinized pu' p is obtained by heat ng for one hour. The fibers still retain their structure in large part but are intimately mixed and coated with glatinized cellulose. The pulpy mass is next passed to a paper machine or board machine. and there is shaped into a sheet or board of the required thickness. The material is still very wet when it comes from the press roll of the paper machine, and in that condition may be regarded as consisting essentially of a skeleton of loosely interlaced cellulose fibers, the interstices between the fibers beingfilled in with the gel that has resulted from complete or partial gelatmization of some of the cellulose fibers. The material is not porous in the sense that there are holes or openings extending in irregular manner through it. but it is porous in the sense that electrolytic salts readily penetrate into and through the gel, and so can be transferred readily from one s de to the other of the battery board. The board is preferably used in the wet condition in which it comes from the press roll of'the paper machine. As an example, a battery travels, on the paper machine to about 1 acrossv the sheet. I

I do not intend to limit myself to the above degree of gelatinization, nor to the dimensions set forth above, and have given said information only by way of-illustra- 'tion.

A battery liner produced as above described is very tough and stronrr while wet, being in this respect markedly different from ordinary battery board, It has no pores or interstices through which fine particles of the mix can filter into contact with the z nc. When the mix is being tamped into the zinc cup which serves the double function of electrode. and container, there is less danger of tearing the paper lining, and what is perhaps more important, there is less danger of air pockets or imperfect contact between the paper lining and the zinc surface. The electrolytic salts read ly diffuse from the mix into the paper partition,

and that diffusion is much more prompt, and much more uniform than with battery boards made in usual manner. All of these features contribute to an increase in the flash or short circuit amperage of the dry cell, and that increase according to my exper ence is to 40% over the flash of standard size cells as ordinarily constructed. The recuperation of the cell after heavy demands on it is more prompt because of the greater speed and the greater uniformitv with which the electrolyte travels through the gelatinous barrier. The uniformity of the board tends toward even distribution of electrolytic act on on the zinc with less likelihood of pitting; and there is more eflicient life for the cell over a period of months, whether on intermittent service or merely standing idle on. the shelf of a dealer.

Although the ,above description has been directed particularly to the production of these improved battery liners from a cooked wood'pulp, such as a spruce sulphite pulp, I am aware that other cellulosic material can be used, for I have found that the raw material may consist of either cellulose as such or combined with lignin and other natural inc-rusting materials, though n the latter case, the beating or other operation fib for effecting mechanical dislntegratlon and chemical change to gelatinized cellulose must be of a more drastic characterbecause of the greater difiiculty of producing there retain their fibrous form, the gelatinization,

by more prolonged beating, may be carried on until substantially all of the fibers have been converted into a structureless gelatinous mass. Such a mass does not have enough strength for use as a battery liner, but that deficiency can be supplied by adding to it fibers that have not passed through the disintegrating treatment in the beater. For example, I have found that a satisfactory battery liner can be made b gelatinizing a portionof the sulphite pu p to the point where it approaches a structureless mass, then adding some of the ori inal fibrous pulp to give the board strengti in the wet condition, then intimately mixing the whole, and ultimately shaping it into boards or liners. When the latter method of manufacture is employed, the fibers added to the structureless mass need not be of the same quality nor even of the same origin as the fibers supplied tothe heater, for gelatinization. produced by grinding wood, and, therefore, containing much lignin and. other incrusting materials. They can even be of mineral or animal. origin, such as asbestos wool, or

hair, or mixtures of these with one another,

or with cellulosic or woody materials. lVhatever fibers are used as the fibrous filler, the final product when ready for assembly in a dry cell is well cemented together with the colloidal gel resultant from mechanically disintegrating cellulose in water until its fibrous structure is radically altered by gelatini zation.

As above indicated the battery liner can best be used while still wet with residual liquor from the gelatinizing operation.

The method herein disclosed is claimed in my divisional application, Serial No. 741,- 287, filed Oct. 2, 1924, entitled Method of manufacturing battery liners.

I claim: 1. A battery liner consisting of interlaced fibers interspersed with gelatinized cellulose and the residual liquorfrom the operation of mechanically disintegrating cellulose in water. I

2. A battery liner consisting for the most part of cellulose fibers and gelatinized cellulose, substantially as described.

3. A battery liner consisting for the most part of appreciably gelatinlzed cellulose ers.

v 4. A battery liner consisting for the most part of partially gelatinized fibers.

5. A battery liner consisting for the most part of partially gelatinized bers, and re sidual liquor from the operation of mechanical disintegration in water.

6. A battery liner consisting for the most part of partially gelatinized cellulose fibers l interspersed with cellulose gel and residual liquor, substantially as described.

7. A battery liner consisting essentially of ungelatinizable fibers, and partially gelatinized cellulose fibers interspersed 'with a cellulose gel and with residual liquor from the operation of mechanically disintegrating cellulose in water.

8. A battery liner comprising mineral fibers and partially gelatinized cellulosic fibers interspersed with a cellulose gel, substantially as described.

In testimony whereof I allix my signature.

ARLIE WILLIAM SCHORG ER. 

